Lymphocyte dynamics in lymph nodes are governed by environmental GO signals and STOP signals that interact with intrinsic polarity networks in the cell. Chemokine receptors are a major class of G-protein coupled receptors and CCR7 is the most important member of this class of receptors for delivering GO signals to naive effector T cells (Teff) in secondary lymphoid tissues. Each antigen receptor can interact with a spectrum of MHC-peptide complex ligands that vary in potency and can be presented over a wide range of concentrations on varying numbers of dendritic cells to deliver STOP signals. Signaling to polarity networks is mediated in part by protein kinase C- 8 (PKC-8), which induces symmetry breaking and conversion of stable synapses to mobile kinapses. While Teff cells activate PKC-8 in response to antigen, regulatory T cells (Treg) inactivate PKC-8 in response to antigen, suggesting distinct control of polarity by TCR signals. Our hypothesis is that particular configuration of GO and STOP and Treg PKC-8 signals lead to failure of peripheral tolerance to low potency ligands that can become autoantigens in the context of tissue injury or inflammatory stimuli. First, we will determine the effect of eliminating GO signals on Teff responses to a spectrum of ligands for a well-studied T cell receptor system. Second, we will examine the structural aspects of T cell responses to high and low potency ligands and quantify the impact of antigen presenting dendritic cell frequency on tolerance induction. Third, we will investigate the role of PKC-8 in control of Treg interactions with DC and Teff in vivo and in vitro. The results of these studies will fill major gaps in our understanding of how Teff and Treg interactions are regulated in lymph nodes and at effector sites, which is key maintaining peripheral tolerance and preventing autoimmunity.